1. Field of the Invention
The present invention relates to an apparatus for controlling the idling of an engine, and more particularly, to a controlling apparatus for reducing variation in the rotational speed of an engine at the time of idling.
2. Description of the Prior Art
In an engine control system which employs a fuel injector as a means for supplying an engine with fuel, the quantity of air being sucked into an engine and the rotational speed of the engine are detected periodically, and the amount of fuel to be supplied to the engine is determined on the basis of the so detected values. The amount of fuel to be supplied is controlled by controlling the width of pulses that make commands regarding the injection of fuel to the fuel injector. The pulse width Tp is obtained by dividing the detected quantity Qa of air by the detected engine speed N. It therefore shows a change in accordance with variations in the quantity of air being sucked in.
The rotational speed of a motor vehicle engine at the time of an idling is as low as approximately 800 rpm, and the air being sucked in at such time has a pulsation. Detection of the quantity of air being sucked into the engine is performed periodically on this pulsating air, and the quantity of air detected accordingly fluctuates considerably. If the detected value representing the quantity of air being sucked in is used as it is to calculate the fuel injection pulse width, the pulse width shows large variations, thereby causing the rotational speed of the engine to fluctuate considerably in accordance with the pulsation in the quantity of air being sucked in. This fluctuation in the engine speed causes vibration or swell, and generates noise. Attempts have therefore been made to reduce variation in the detected values by conducting filtering of the detected values for the quantity of air being sucked in. However, although the variation in the detected values representing the quantity of air being sucked in is reduced through filtering, the detected values representing the engine speed still vary, and the variations in the fuel injection pulse width cannot be reduced. Thus variation in the rotational speed of the engine cannot be adequately reduced and vibration and noise is accordingly generated.